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Abstract:

Exemplary embodiments are provided of multiple-antenna systems with
enhanced and/or good isolation and directivity. In one exemplary
embodiment, a system generally includes a ground plane and two or more
antenna elements coupled to the ground plane. The system also includes
two or more low frequency isolators/reflectors and two or more high
frequency isolators/reflectors coupled to the ground plane.

Claims:

1. A system comprising: a ground plane two or more antenna elements
coupled to the ground plane; two or more low frequency
isolators/reflectors coupled to the ground plane; and two or more high
frequency isolators/reflectors coupled to the ground plane.

2. The system of claim 1, wherein each antenna element is configured for
multi-band operation such that each antenna element is operable within a
first frequency range and a second frequency range.

3. The system of claim 2, wherein: the first frequency range is from
about 2.4 gigahertz to about 2.5 gigahertz, and the second frequency
range is from 4.9 gigahertz to 5.875 gigahertz; and/or the first
frequency range is the 2.45 gigahertz band, and the second frequency
range is the 5 gigahertz band.

4. The system of claim 1, wherein: the low frequency isolators/reflectors
have inverted U-shaped configurations; and/or the high frequency
isolators/reflectors have inverted U-shaped configurations.

5. The system of claim 1, wherein: each of the low frequency
isolators/reflectors includes two vertical sections and a horizontal
section that is generally parallel with the ground plane; and each of the
high frequency isolators/reflectors includes two vertical sections and a
horizontal section that is generally parallel with the ground plane.

6. The system of claim 1, wherein the low frequency isolators/reflectors
and high frequency isolators/reflectors are positioned relative to the
antenna elements for increasing isolation between the antenna elements
and/or for increasing directivity of each said antenna element in the
direction of the sector that said antenna element serves.

7. The system of claim 1, wherein the antenna includes: three antenna
elements, three low frequency isolators/reflectors, and three high
frequency isolators/reflectors; or six antenna elements, six low
frequency isolators/reflectors, and six high frequency
isolators/reflectors.

8. The system of claim 1, further comprising two or more coaxial cables
coupled to the two or more antenna elements, respectively, for feeding
the antenna elements.

9. The system of claim 1, wherein each antenna element comprises first
and second radiating arms and a feeding element, the first and second
radiating arms and feeding element comprising electrically-conductive
traces on the same side of a circuit board.

10. The system of claim 1, wherein the antenna elements comprise one or
more of a monopole antenna, an inverted F antenna (IFA), and/or a planar
inverted F antenna (PIFA).

11. The system of claim 1, wherein the high and low frequency
isolators/reflectors are configured to be operable as both isolators and
reflectors.

12. The system of claim 1, wherein the antenna includes the same number
of antenna elements, low frequency isolators/reflectors, and high
frequency isolators/reflectors.

13. The system of claim 1, wherein: the ratio of antenna elements to low
frequency isolators/reflectors is one-to-one; and/or the ratio of antenna
elements to high frequency isolators/reflectors is one-to-one; and/or the
ratio of low frequency isolators/reflectors to high frequency
isolators/reflectors is one-to-one.

14. The system of claim 1, wherein the system is a multiple input
multiple output (MIMO) antenna system.

15. The system of claim 1, wherein: the antenna elements are mounted to
the ground plane along a circumference of a circular portion of the
ground plane such that the antenna elements are equidistant from a center
of the circular portion of the ground plane and such that the antenna
elements are spaced equally apart from each other and such that a one
hundred twenty degree (120.degree.) arc is defined between the mounting
points of two adjacent antenna elements and the center of the circular
portion of the ground plane; and/or the low frequency
isolators/reflectors are in a spoked configuration centered at the center
of the circular portion of the ground plane, such that the low frequency
isolators/reflectors are positioned about the center of the circular
portion of the ground plane and extend outwardly in a direction away from
the center of the circular portion of the ground plane; and/or each of
the high frequency isolators/reflectors is between a corresponding one of
the antenna elements and the center of the circular portion of the ground
plane.

16. The system of claim 15, wherein the circular portion of the ground
plane is an imaginary or reference circle on a surface of the ground
plane.

17. A system comprising: a ground plane including a circular portion
having a circumference and a center; a plurality of antenna elements
mounted to the ground plane along the circumference of the circular
portion of the ground plane, the antenna elements equidistant from the
center of the circular portion of the ground plane, the antenna elements
spaced equally apart from each other such that a one hundred twenty
degree (120.degree.) arc is defined between mounting points of two
adjacent antenna elements and the center of the circular portion of the
ground plane; a plurality of low frequency isolators/reflectors in a
spoked configuration centered at the center of the circular portion of
the ground plane, such that the low frequency isolators/reflectors are
positioned about the center of the circular portion of the ground plane
and extend outwardly in a direction away from the center of the circular
portion of the ground plane; and/or a plurality of high frequency
isolators/reflectors, each placed between a corresponding one of the
antenna elements and the center of the circular portion of the ground
plane.

18. The system of claim 17, wherein: each of the low frequency
isolators/reflectors include two vertical sections and a horizontal
section that is generally parallel with the ground plane, and defining an
inverted U-shaped configuration for each of the low frequency
isolators/reflectors; and each of the high frequency isolators/reflectors
include two vertical sections and a horizontal section that is generally
parallel with the ground plane, and defining an inverted U-shaped
configuration for each of the high frequency isolators/reflectors.

19. The system of claim 17, wherein: the circular portion of the ground
plane is an imaginary or reference circle on a surface of the ground
plane; and/or the antenna includes the same number of antenna elements,
low frequency isolators/reflectors, and high frequency
isolators/reflectors, such that the ratio of antenna elements to low
frequency isolators/reflectors is one-to-one and such that the ratio of
antenna elements to high frequency isolators/reflectors is one-to-one.

20. A multiple input multiple output (MIMO) antenna system, the antenna
system comprising: two or more antenna elements; and two or more
isolators/reflectors positioned relative to the antenna elements for
increasing isolation between the antenna elements and for increasing
directivity of each said antenna element in the direction of the sector
that said antenna element serves.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of PCT International Application
No. PCT/MY2010/000125 filed on Jul. 19, 2010 (now published as WO
2012/011796, published on Jan. 26, 2012). The entire disclosure of the
above application is incorporated herein by reference.

FIELD

[0002] The present disclosure generally relates to multiple-antenna
systems with enhanced and/or good isolation and directivity.

BACKGROUND

[0003] This section provides background information related to the present
disclosure which is not necessarily prior art.

[0004] Multiple-antenna radio systems generally use multiple antennas at
the transmitter and/or receiver to improve communication performance.
Such multiple-antenna systems are commonly referred to or known as
Multiple Input Multiple Output (MIMO) antenna systems. Multiple-antenna
radio systems are commonly used in wireless communications, because these
systems may offer significant increases in data throughput and link range
without additional bandwidth or transmit power.

SUMMARY

[0005] This section provides a general summary of the disclosure, and is
not a comprehensive disclosure of its full scope or all of its features.

[0006] According to various aspects, exemplary embodiments are disclosed
of multiple-antenna systems having enhanced and/or good isolation and
directivity. In an exemplary embodiment, an antenna system generally
includes a ground plane and two or more antenna elements coupled to the
ground plane. The system also includes two or more low frequency
isolators/reflectors and two or more high frequency isolators/reflectors
coupled to the ground plane.

[0007] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples in
this summary are intended for purposes of illustration only and are not
intended to limit the scope of the present disclosure.

DRAWINGS

[0008] The drawings described herein are for illustrative purposes only of
selected embodiments and not all possible implementations, and are not
intended to limit the scope of the present disclosure.

[0009] FIG. 1 is a perspective view of a multiple-antenna system having
three antenna elements, three high frequency isolators/reflectors, and
three low frequency isolators/reflectors according to an exemplary
embodiment of the present disclosure, where the internal antenna
components (typically covered and hidden from view by a radome) are shown
for clarity;

[0010] FIG. 1A is a perspective view of the multiple-antenna system shown
in FIG. 1 and exemplary coaxial cables feeding the antenna elements
according to an exemplary embodiment;

[0011] FIGS. 2A and 2B are exemplary line graphs illustrating isolation in
decibels versus frequency (in gigahertz) measured for a prototype of the
multiple-antenna system shown in FIG. 1 with isolators/reflectors (FIG.
2A) and without isolators/reflectors (FIG. 2B), respectively;

[0012] FIGS. 3A and 3B illustrate exemplary azimuth plane radiation
patterns measured for the three antenna elements of a prototype of the
multiple-antenna system shown in FIG. 1 at a frequency of 2.45 gigahertz
(FIG. 3A) and 5.47 gigahertz (FIG. 3B);

[0013]FIG. 4 is a perspective view of another exemplary embodiment of a
multiple-antenna system having six antenna elements, six high frequency
isolators/reflectors, and six low frequency isolators/reflectors, where
the internal antenna components (typically covered and hidden from view
by a radome) are shown for clarity; and

[0014] FIG. 5 illustrates exemplary azimuth plane radiation patterns
measured for the six antenna elements of a prototype of the
multiple-antenna system shown in FIG. 4 at a frequency of 5.35 gigahertz.

DETAILED DESCRIPTION

[0015] Example embodiments will now be described more fully with reference
to the accompanying drawings.

[0016] In multiple-antenna systems, multiple antennas are used to improve
transmission robustness and/or increase transmission rate. Generally,
multiple antennas for multiple input multiple output (MIMO) systems
perform well under the condition that the antennas have low cross
correlation in different schemes namely spatial scheme, pattern scheme,
and polarization scheme. For economical reasons during design and
manufacturing, the multiple antennas are usually of identical design.
With the market trend towards smaller and more compact devices, the
decreasing overall size of the device means that the antennas are being
increasingly put closer and closer together. But having multiple antennas
in close proximity results in poor isolation between the antennas, which,
in turn, decreases the performance of the radio system. For example, the
inventors have recognized that because the antennas are usually of
identical design for a multiple-antenna system, the radiation patterns
might overlap with equal antenna gain. In which case, stability might
become an issue when the radio system constantly switches back and forth
between the antennas.

[0017] Accordingly, the inventors have disclosed herein multiple-antenna
systems including multiple antennas and multiple isolators/reflectors to
enhance the isolation between antennas and at the same time increase the
directivity of the individual antenna elements. In various exemplary
embodiments, each antenna element has a sector-shaped radiation pattern
with an equally-divided coverage sector angle such that the sum of all
sector angles for the antenna elements equals the total coverage angle
required. This is considered to be utilizing the pattern scheme that
offers higher capacity and longer range for the systems.

[0018] In various exemplary embodiments, a system includes a one-to-one
ratio of antenna elements to the high frequency isolators/reflectors and
to the low frequency isolators/reflectors. That is, these exemplary
embodiments include the same number of antenna elements, high frequency
isolators/reflectors, and low frequency isolators/reflectors. For
example, the inventors have disclosed exemplary embodiments (e.g., system
100 (FIG. 3), etc.) that includes three antenna elements, three high
frequency isolators/reflectors, and three low frequency
isolators/reflectors. The inventors have also disclosed exemplary
embodiments (e.g., system 200 (FIG. 4), etc.) that includes six antenna
elements, six high frequency isolators/reflectors, and six low frequency
isolators/reflectors. Other exemplary embodiments may include more or
less antenna elements, high frequency isolators/reflectors, and/or low
frequency isolators/reflectors, as a system may be scaled (e.g., two
antennas, four antennas, five antennas, seven antennas, etc.) accordingly
depending on the particular requirements of the intended application or
end-use. In addition, other exemplary embodiments need not include a
one-to-one ratio or equal/same number of antenna elements, high frequency
isolators/reflectors, and/or low frequency isolators/reflectors. For
example, other exemplary embodiments may include a number of high
frequency isolators/reflectors and/or low frequency isolators/reflectors
equal to, greater than, or less than the number of antenna elements.

[0019] In various exemplary embodiments, a system includes multiple
antenna elements and multiple isolators/reflectors. The
isolators/reflectors may be positioned relative to the antenna elements
to increase isolation between the antenna elements and/or increase
directivity of each antenna element in the direction of the sector that
the particular antenna element serves. The multiple isolators/reflectors
may include one or more combined high frequency and low frequency
isolators/reflectors. Additionally, or alternatively, the multiple
isolators/reflectors may include one or more high frequency
isolators/reflectors that are separate and/or spaced apart from one or
more low frequency isolators/reflectors. By way of example only, a low
frequency isolators/reflector may be configured to be operable with
frequencies falling within the 2.45 gigahertz band (from 2.4 gigahertz to
2.5 gigahertz), and a high frequency isolators/reflector may be
configured to be operable with frequencies falling within the 5 gigahertz
band (from 4.9 gigahertz to 5.875 gigahertz). These frequencies are only
examples, however, as aspects of the present disclosure are not limited
solely to these two frequency bands.

[0020] In one particular exemplary embodiment, an antenna system includes
three antenna elements configured for operation in a high frequency band
and low frequency band. Isolators/reflectors are mounted vertically over
a ground plane. The antenna elements are placed equidistant from the
center of a circular portion of the ground plane, which circular portion
may simply be an imaginary or reference circle that is imagined or
defined on the top surface of the ground plane for reference purposes.
The mounting point of the antenna elements are on the circumference of
the circular portion or imaginary circle on the ground plane. The antenna
elements are spaced equally apart, so that a one hundred twenty degree
(120°) arc is formed or defined between the mounting point of two
adjacent antenna elements and the center of the imaginary circle or
circular portion on the ground plane. Three inverted U shaped low
frequency isolators/reflectors are placed in a star-shaped configuration
centered at the center of the imaginary circle or circular portion on the
ground plane. Another three inverted U shaped high frequency
isolators/reflectors are each placed adjacent a corresponding one of the
antenna element between that antenna element and the center of the
imaginary circle or circular portion on the ground plane. The antenna
elements may be of any type suitable, such as a monopole antenna, an
inverted F antenna (IFA), planar inverted F antenna (PIFA), etc. The
inverted U shaped elements are operable as both isolators and reflectors.
The frequency at which each upside down or inverted U shaped element is
effective is determined primarily by the length of the horizontal section
of the upside down or inverted U shaped element. With this exemplary
disclosed embodiment, the isolation between the antenna elements was
increased (e.g., by about seven percent to about ten percent, etc.). This
increased isolation allows for more antenna elements to be put in the
same volume of space and/or allows the same number of antennas to be put
in a smaller volume of space. This example embodiment also allows for
increased directivity of each antenna element in the direction of the
sector that the particular antenna element serves. In turn, this will
help improve radio stability and increase receive-sensitivity extending
the range of the radio transmission.

[0021] With reference now to the figures, FIG. 1 illustrates an exemplary
embodiment of a multiple-antenna system 100 embodying one or more aspects
of the present disclosure. As shown, the antenna system 100 includes
three antenna elements 104, 108, 112, three low frequency
isolators/reflectors 116, 120, 124, and three high frequency
isolators/reflectors 128, 132, 136. The antenna elements and
isolators/reflectors are mounted on or to the ground plane 140 in a
generally vertical orientation and perpendicularly relative to the ground
plane 140.

[0022] This particular system 100 is configured for use as tri-sectorial
multiple-antenna system (e.g., MIMO antenna system), although aspects of
the present disclosure are not limited solely to tri-sectorial and/or
MIMO antenna systems. And, each antenna element 104, 108, 112 may be
identical to the other antenna elements, or one or more of the antenna
elements may be differently configured (e.g., shaped, sized, different
materials, etc.) than the other antenna elements depending on the
particular end use or application. In addition, each of the low frequency
isolators/reflectors 116, 120, 124 may be identical, or they may be
different from each other. Likewise, each of the high frequency
isolators/reflectors 128, 132, 136 may be identical, or they may be
different from each other.

[0023] With continued reference to FIG. 1, each antenna element 104, 108,
112 includes, and/or is supported by, a substrate, such as substrate 105,
109, 113. The substrates 105, 109, and/or 113 may be a rigid insulator,
such as a circuit board substrate (e.g., Flame Retardant 4 or FR4, etc.),
plastic carrier, etc. Alternatively, the substrates 105, 109, and/or 113
may be a flexible insulator, such as a flexible circuit board, flex-film,
etc. The antenna elements 104, 108, 112 may include
electrically-conductive material (e.g., copper, gold, silver, alloys,
combinations thereof, other electrically-conductive materials, etc.) in
the form of traces 106, 110, 114 on the substrates 105, 109, 113,
respectively. The antenna elements 104, 108, 112 may be single or
multiple layered PCB antennas. Alternatively, the antenna elements 104,
108, 112 (whether mounted on a substrate or not) may be constructed from
sheet metal by cutting, stamping, etching, etc.

[0024] Each antenna element 104, 108, 112 includes a first radiating or
resonant element for a low frequency band (e.g., from 2.4 gigahertz to
2.5 gigahertz, etc.) and a second radiating or resonant element for a
high frequency band (e.g., from 4.9 gigahertz to 5.875 gigahertz, etc.).
The first and second radiating elements of each antenna element 104, 108,
112 may be quarter wavelength (1/4λ) radiating elements, such that
each of the first and second radiating elements is sized to be
approximately one quarter of the wavelength of a desired resonant
frequency. In this particular example, the antenna element 104 includes a
first low frequency arm 107 and a second high frequency arm 110. In this
exemplary embodiment, the high frequency arms are shorter than the low
frequency arms. The arms or elements are folded (e.g., spiral shaped,
etc.), bent, and/or turned to help reduce the overall size. Antennas
according to the present disclosure are not limited, however, to the
particular shape, size, configuration, etc. of the antenna elements shown
in FIG. 1. In addition, the frequencies set forth in this paragraph are
only examples, as aspects of the present disclosure are not limited
solely to these two frequency bands.

[0025] The antenna elements 104, 108, and 112 also include feeding
elements and ground points. As shown in FIG. 1, the antenna element 104
includes a feeding element 123 and grounding point 111. In this example,
the bottom of the feeding element 123 may provide a feeding point, for
example, for connection to (e.g., soldering, etc.) a coaxial cable, other
feed, or transmission line. For example, FIG. 1A illustrates an exemplary
embodiment in which coaxial cables 150 are shown feeding the antenna
elements 104, 108, 112 of the antenna 100. In this example illustrated in
FIG. 1A, the coaxial cable 150 includes a braid 125 that is soldered to
the grounding point 111 of the antenna element 104. The coaxial cable 150
also includes a signal center conductor 127 that is soldered to the
feeding point 123 of the antenna element 104. Alternative embodiments may
include other feeding arrangements besides coaxial cable.

[0026] Soldering pads 115 allow the antenna element 104 to be soldered to
the ground plane 140 (e.g., ground plane of PCB, metal sheet, etc.). In
some embodiments, the bottom of the antenna elements 104, 108, 112 may
include downwardly extending tabs that are insertable or positionable
within slots or holes in the ground plane 140 for aligning and
mechanically mounting the antenna elements 104, 108, 112 to the ground
plane 140. Alternative embodiments may include other means for aligning
and/or mechanically mounting an antenna element to a ground plane.

[0027] In this example, the antenna elements 104, 108, 112 are mounted to
the ground plane 140 equidistant from the center of a circular portion on
the ground plane 140, which circular portion may simply be an imaginary
or reference circle that is on top of the ground plane 140 for reference
purposes when mounting the antenna components. In this illustrated
example, the center of the circular portion or imaginary circle coincides
with or is the same as the center of the ground plane 140 in FIG. 1, etc.
The mounting points or location of the antenna elements 104, 108, 112 are
placed along the perimeter or circumference of the imaginary circle or
circular portion on the ground plane 140. The antenna elements 104, 108,
112 are spaced equally apart, so that a one hundred twenty degree
(120°) arc is formed or defined between the mounting point of two
adjacent antenna elements and the center of the imaginary circle or
circular portion on the ground plane 140. Alternative embodiments may
include other mounting arrangements for the antenna elements on the
ground plane.

[0028] The dimensions, shapes, and mounting location (e.g., location of
grounding points, etc.) of the low frequency isolators/reflectors 116,
120, 124 relative to the antenna elements 104, 108, 112 may be determined
(e.g., optimized, etc.) to improve the isolation between the antenna
elements 104, 108, 112. In this particular example shown in FIG. 1, the
low frequency isolators/reflectors 116, 120, 124 are mounted generally
vertically or perpendicularly relative to the ground plane 140. And, the
low frequency isolators/reflectors 116, 120, 124 comprise inverted
U-shaped metallic strips 117 on a substrate 118, which are arranged or
placed in a star-shaped or spoked configuration centered at the center of
the imaginary circle or circular portion on the ground plane 140. In this
example, the substrates 118 are positioned about the center of the ground
plane 140 so as to extend outwardly in a direction away from the center
of the ground plane 140.

[0029] A wide range of materials may be used for any of the substrates
disclosed herein. By way of example, the low frequency
isolators/reflectors 116, 120, 124 may include, and/or be supported by,
substrates 118 comprising a rigid insulator, such as a circuit board
substrate (e.g., Flame Retardant 4 or FR4, etc.), plastic carrier, etc.
Alternatively, the substrates 118 may be a flexible insulator, such as a
flexible circuit board, flex-film, etc. The inverted U shaped strips 117
on the substrates 118 may include electrically-conductive material (e.g.,
copper, etc.) in the form of traces on the substrates 118. The low
frequency isolators/reflectors 116, 120, 124 (whether mounted on a
substrate or not) may be constructed from sheet metal by cutting,
stamping, etching, etc.

[0030] In this particular example, the low frequency isolators/reflectors
116, 120, 124 include the inverted U shaped strips 117 that are operable
as both isolators and reflectors. The frequency at which each upside down
or inverted U shaped strip 117 is effective is determined primarily by
the length of the horizontal section 119 of the upside down or inverted U
shaped element 117. The horizontal section 119 is generally parallel to
the top surface of the ground plane 140 in this illustrated embodiment.
The inverted U shaped element 117 also includes two vertical legs or
grounding stubs 121 for electrically connecting to the ground plane 140.
Alternative embodiments may include one or more isolators/reflectors with
a different configuration (e.g., different shape, size, mounting
location, etc.), such as L-shaped isolator/reflector.

[0031] In addition, the low frequency isolators/reflectors 116, 120, 124
may also include tabs along the bottom thereof. The tabs may be
configured to be inserted or positioned within slots or holes 122 in the
ground plane 140 for aligning and mechanically mounting the low frequency
isolators/reflectors 116, 120, 124. Alternative embodiments may include
other means for aligning and/or mechanically mounting an
isolator/reflector to a ground plane.

[0032] The dimensions, shapes, and mounting location (e.g., location of
grounding points, etc.) of the high frequency isolators/reflectors 128,
132, 136 relative to the antenna elements 104, 108, 112 may be determined
(e.g., optimized, etc.) to improve the isolation between the antenna
elements 104, 108, 112. In this particular example, the high frequency
isolators/reflectors 128, 132, 136 are mounted generally vertically or
perpendicularly relative to the ground plane 140. Each high frequency
isolators/reflectors 128, 132, 136 is between the center of the ground
plane 140 and a corresponding one of the antenna elements 104, 108 112.
And, the high frequency isolators/reflectors 128, 132, 136 comprise
inverted U-shaped metallic strips having end portions 130 electrically
connected and mounted (e.g., soldered, etc.) to the ground plane 140. The
illustrated high frequency isolators/reflectors 128, 132, 136 do not
include any substrates supporting the inverted U-shaped metallic strips.
Instead, the inverted U-shaped metallic strips have end portions 130 that
are mounted to the ground plane 140 such that the horizontal and vertical
portions 131, 133 are free-standing. Alternative embodiments may include
a different configuration (e.g., different shape, size, mounting
location, etc.) for one or more of the high frequency
isolators/reflectors. For example, another exemplary embodiment may
include one or more high frequency isolators/reflectors that include a
substrate, such as a rigid insulator (e.g., plastic carrier, a circuit
board substrate like Flame Retardant 4 or FR4, etc.) or a flexible
circuit board, flex-film, etc.

[0033] In this particular example, the high frequency isolators/reflectors
128, 132, 136 include the inverted U shaped strips that are operable as
both isolators and reflectors. The frequency at which each upside down or
inverted U shaped strip is effective is determined primarily by the
length of the horizontal section 131 of the upside down or inverted U
shaped element. The horizontal section 131 is generally parallel to the
top surface of the ground plane 140 in this illustrated embodiment.

[0034] In addition, the low frequency isolators/reflectors 116, 120, 124
may also include tabs along the bottom thereof. The tabs may be
configured to be inserted or positioned within slots or holes 122 in the
ground plane 140 for aligning and mechanically mounting the low frequency
isolators/reflectors 116, 120, 124.

[0035] The ground plane 140 is shown as a circular metal plate.
Alternative embodiment may include a ground plane having a different
configuration, such as a ground plane with a different shape (e.g.,
non-circular etc.), different size (e.g., larger or smaller relative to
the other components of the antenna 100), different materials, etc.

[0036] FIGS. 2A, 2B, 3A, and 3B illustrate analysis results measured for a
prototype of the multiple-antenna system 100 shown in FIG. 1. These
analysis results shown in FIGS. 2A, 2B, 3A, and 3B are provided only for
purposes of illustration and not for purposes of limitation. More
specifically, FIGS. 2A and 2B are exemplary line graphs illustrating
isolation in decibels versus frequency (in gigahertz) measured for a
prototype of the multiple-antenna system shown in FIG. 1 with
isolators/reflectors (FIG. 2A) and without isolators/reflectors (FIG.
2B), respectively. FIGS. 3A and 3B illustrate exemplary azimuth plane
radiation patterns measured for the three antenna elements of a prototype
of the multiple-antenna system shown in FIG. 1 at a frequency of 2.45
gigahertz (FIG. 3A) and 5.47 gigahertz (FIG. 3B). Generally, these
analysis results show that the isolation between the antenna elements
104, 108, 112 was increased by about seven percent to about ten percent,
and show the increased directivity of each antenna element in the
direction of the sector that the particular antenna element serves.

[0037]FIG. 4 illustrate another exemplary embodiment of a
multiple-antenna system 200 embodying one or more aspects of the present
disclosure. In this particular example, the antenna 200 includes six
antenna elements 204, six low frequency isolators/reflectors 216, six
high frequency isolators/reflectors 228, and a ground plane 240. The
components of the antenna 200 may be similar to the antenna 100 described
above.

[0038] FIG. 5 illustrates analysis results measured for a prototype of the
multiple-antenna system 200 shown in FIG. 4. These analysis results shown
in FIG. 5 are provided only for purposes of illustration and not for
purposes of limitation. More specifically, FIG. 5 illustrates exemplary
azimuth plane radiation patterns measured for the six antenna elements
204 of a prototype of the multiple-antenna system 200 shown in FIG. 4 at
a frequency of 5.35 gigahertz.

[0039] Numerical dimensions and values are provided herein for
illustrative purposes only. The particular dimensions and values provided
are not intended to limit the scope of the present disclosure.

[0040] Spatially relative terms, such as "inner," "outer," "beneath",
"below", "lower", "above", "upper" and the like, may be used herein for
ease of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. Spatially
relative terms may be intended to encompass different orientations of the
device in use or operation in addition to the orientation depicted in the
figures. For example, if the device in the figures is turned over,
elements described as "below" or "beneath" other elements or features
would then be oriented "above" the other elements or features. Thus, the
example term "below" can encompass both an orientation of above and
below. The device may be otherwise oriented (rotated 90 degrees or at
other orientations) and the spatially relative descriptors used herein
interpreted accordingly.

[0041] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be limiting.
As used herein, the singular forms "a", "an" and "the" may be intended to
include the plural forms as well, unless the context clearly indicates
otherwise. The terms "comprises," "comprising," "including," and
"having," are inclusive and therefore specify the presence of stated
features, integers, steps, operations, elements, and/or components, but
do not preclude the presence or addition of one or more other features,
integers, steps, operations, elements, components, and/or groups thereof.
The method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the particular
order discussed or illustrated, unless specifically identified as an
order of performance. It is also to be understood that additional or
alternative steps may be employed.

[0042] When an element or layer is referred to as being "on", "engaged
to", "connected to" or "coupled to" another element or layer, it may be
directly on, engaged, connected or coupled to the other element or layer,
or intervening elements or layers may be present. In contrast, when an
element is referred to as being "directly on," "directly engaged to",
"directly connected to" or "directly coupled to" another element or
layer, there may be no intervening elements or layers present. Other
words used to describe the relationship between elements should be
interpreted in a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the term
"and/or" includes any and all combinations of one or more of the
associated listed items.

[0043] Although the terms first, second, third, etc. may be used herein to
describe various elements, components, regions, layers and/or sections,
these elements, components, regions, layers and/or sections should not be
limited by these terms. These terms may be only used to distinguish one
element, component, region, layer or section from another region, layer
or section. Terms such as "first," "second," and other numerical terms
when used herein do not imply a sequence or order unless clearly
indicated by the context. Thus, a first element, component, region, layer
or section discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of the
example embodiments.

[0044] Example embodiments are provided so that this disclosure will be
thorough, and will fully convey the scope to those who are skilled in the
art. Numerous specific details are set forth such as examples of specific
components, devices, and methods, to provide a thorough understanding of
embodiments of the present disclosure. It will be apparent to those
skilled in the art that specific details need not be employed, that
example embodiments may be embodied in many different forms and that
neither should be construed to limit the scope of the disclosure. In some
example embodiments, well-known processes, well-known device structures,
and well-known technologies are not described in detail.

[0045] The disclosure herein of particular values and particular ranges of
values for given parameters are not exclusive of other values and ranges
of values that may be useful in one or more of the examples disclosed
herein. Moreover, it is envisioned that any two particular values for a
specific parameter stated herein may define the endpoints of a range of
values that may be suitable for the given parameter. The disclosure of a
first value and a second value for a given parameter can be interpreted
as disclosing that any value between the first and second values could
also be employed for the given parameter. Similarly, it is envisioned
that disclosure of two or more ranges of values for a parameter (whether
such ranges are nested, overlapping or distinct) subsume all possible
combination of ranges for the value that might be claimed using endpoints
of the disclosed ranges.

[0046] The foregoing description of the embodiments has been provided for
purposes of illustration and description. It is not intended to be
exhaustive or to limit the invention. Individual elements or features of
a particular embodiment are generally not limited to that particular
embodiment, but, where applicable, are interchangeable and can be used in
a selected embodiment, even if not specifically shown or described. The
same may also be varied in many ways. Such variations are not to be
regarded as a departure from the invention, and all such modifications
are intended to be included within the scope of the invention.